This invention relates to engine protection systems. More particularly, this invention relates to such systems which prevent the starting or operation of an engine when a low oil condition is sensed.
Many ways are known for stopping an internal combustion engine when a low oil level or low oil pressure is sensed during engine operation. Some of these devices cut off the fuel to stop the engine. See U.S. Pat. Nos. 2,259,047 issued Oct. 14, 1941 to Scott, Jr., and U.S. Pat. No. 4,102,316 issued Jul. 25, 1978 to Valbert. Other prior art devices interrupt engine ignition to shut off the engine when a low oil pressure condition is sensed. See U.S. Pat. No. 2,499,319 issued Feb. 8, 1950 to Lillquist.
These engine shut off devices typically require expensive valves or switches and additional wiring.
However, it is also desirable to prevent the engine from starting altogether to minimize engine damage if a low oil condition is sensed. Several techniques are known for preventing the starting of the engine under these circumstances. One typical prior art technique is to use a float, having an electrical contact, that floats in the engine crankcase oil. When the oil level becomes too low, the contact on the float makes an electrical connection with an electrical contact attached to the engine frame to ground the ignition pulses.
Such float-type oil level sensors are expensive since they contain several mechanical parts, additional wiring, and an electrical switch.
It is therefore desirable to provide a simple, inexpensive low oil sensor that prevents engine starting or engine operation when the oil level is below a predetermined level.